The total pyridine nucleotide(PN) and the oxidized and reduced nicotinamide adenine dinucleotide (NAD, NADH) were determined in the liver, heart, brain and intestine of the chick embryo. The effect of administration of nicotinamide and nicotinic acid, both the precursor of the pyridine nucleotides, also was studied.
In each of all examined organs, the concentrations of PN, NAD and NADH were remained at constant throughout the pre-hatching period. At immediately after the hatching, however, only heart and intestine maintained the pre-hatching levels while ;the liver showed decreases of all three examined nucleotides. The content of NAD and NADH in brain after the hatching increased.
The injection of nicotinamide made the concentrations of PN and NAD in embryonic liver twice as that of the untreated control while the nicotinic acid did not exery any change. The latter, however, introduced a slight increment of PN and NAD in the liver posthatching and adult chicks.
The content of NADH in the examined organs was extremely low during the development being about 5 to 10% of that of NAD level.
The relationship of these findings to those of mammalian tissues was discussed.
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